It is known to provide a vibratory conveying structure to separate composite mixtures including particles of different size and density. An exemplary use for such a structure is to separate accumulated materials in a wood yard. The composite mixture in this instance may include wood fiber, dirt, stones, steel, and/or other materials that commonly are found around such an operation. Other composite mixtures may include glass, plastic, paper, metal, or other materials.
A typical conveying structure may use a vibrating trough to advance the composite mixture from a supply source to a discharge area. The flow path along the trough is interrupted by a drop out opening. The composite mixture is directed from a first plateau across the drop out opening so that the trajectory of certain of the particles is intercepted by a landing surface at the discharge side of the drop out opening and beneath the elevation of the first plateau. A fixed width forced air supply is directed through the flow path and propels additional low density particles onto the landing surface or second plateau. The more dense particles fall to the bottom of the structure for accumulation in a first area while the particles on the landing surface are conveyed, typically by a vibratory force, to a second, separate area.
In some previous systems, the air supply impinging on the particles falling off of the first plateau into the drop out opening was ineffective in propelling the desired lower density particles to the landing area. For example, in some systems, the particles lodged together as clumps so that the force of the fixed width air stream was not sufficient to cause the particles to reach the landing area, though their individual weight dictated that they should follow the path of the low density material. As a result, sometimes an incomplete separation occurred. To attempt to break up the clumps, the air flow velocity was sometimes increased with a typical result that heavy unwanted particles were propelled across the drop out opening and onto the landing area.
In other systems, to attempt to break up the clumps, a foraminous fluidizing deck was provided in the conveying plateau adjacent the drop out opening for directing an air supply upward through the fluidizing deck. Air forcibly delivered through the fluidizing deck tended to aid in the initial break up of lumped particles, before the composite mixture entered the main air stream directed through the drop out opening.
However, in some instances, even the combination of a fluidizing deck and a fixed width main air stream proved ineffective in propelling the desired particles to the landing area. For example, in some instances, the composition of the particles varied depending upon initial make-up of the mixture, and/or depending upon the particular environment within which the apparatus operated. Thus, in some circumstances, the set up conditions of the fluidizing deck and the air stream were calibrated for the average composite mixture, and were sometimes not optimized for each particular mixture, resulting in incomplete separation. Consequently, a vibratory device having improved material separating capabilities is desired.